CarabasFoliage penetration radar

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Carabas is designed to enable superior foliage and camouflage penetration (FOPEN) capabilities, wide area surveillance and automatic target detection. The system is based on low-frequency Synthetic Aperture Radar (SAR) and change detection technology and it also exploits polarimetric sensing.

Monitoring forested areas has always been an important requirement in military operations. Especially since highly maneuverable units often deploy and act from deep concealment in forests or, in open terrain, are concealed by camouflage.

Features

Carabas is designed to enable superior foliage and camouflage penetration (FOPEN ) capabilities, wide area surveillance and automatic target detection. The system is based on low-frequency Synthetic Aperture Radar (SAR) and change detection technology and it also exploits polarimetric sensing. This gives the system a unique ability to detect and pinpoint exact geopositions of potential targets, irrespective of weather and light conditions, as well as through foliage and camouflage.

Supreme penetration performance

Agile and instantly available

Straightforward integration

Automatic target detection

Strong object interaction

Proven performance

Emerging capabilities

Versatile capacity

Supreme penetration performance

Carabas utilses two very broad bands in the low VHF and UHF domains: 20 – 90 MHz and 140 – 360 MHz, respectively. It is the low VHF band that gives Carabas its supreme penetration performance, while the UHF band is more important for detecting smaller targets in lighter vegetation. Carabas's signals penetrate foliage without reflections through all vegetation types and man-made camouflage. The system can sense any concealed ordnance – trucks, tanks,containers, vehicles or artillery – with dimensions around one metre or larger. The location of the ordnance is pinpointed with metre precision.

The physics behind Carabas's unique penetration properties is quite straightforward: radar signals interact with objects of the same size or larger as the radar wavelength. This means that Carabas waves, with wavelengts in the interval 1-15 m, does interact strongly with meter-sized and larger objects (such as vehicles), but does not interact with leaves and branches in forest foliage, nor with camouflage netting.

Agile and instantly available

Carabas is miniaturised to also fit small, light and low footprint aircraft. The system is thus suitable for tactical use providing ground forces with their own self-controlled surveillance capability that is instantly available for missions. In this configuration, Carabas would be installed on a small UAV or helicopter with a typical surveillance capability of 5 sq km per minute at 6 km standoff distance. Scaled to a business jet aircraft the surveillance capacity expands to 5 sq km per second.

Straightforward integration

To achieve on-line and real-time operation using small aircraft, Carabas offers straightforward integration with data links for down-linking radar data to the ground. For larger airborne platforms it is often more efficient to perform the signal and data processing on board.

Automatic target detection

Carabas provides reliable and automated target detection by using advanced change detection methods. When a significant change event occurs, for instance if a vehicle enters a surveyed forest area, a change-detection scheme, comparing a new image to an older one without the vehicle present, will pick up the event automatically, without human interference. The scheme surveys vast ground areas and pinpoints vehicles below the trees and registers barbed wire and tree clearings that signal military or illegal activity. With this method Carabas can also easily detect a fully camouflaged deployment of military units in open terrain.

Strong object interaction

The change detection technology works ideally within the frequency bands used by Carabas since radar signals interact with objects of the same size or larger as the radar wavelength. Therefore, Carabas interacts strongly with man-made objects (typically metre-sized) while microwave radars will also interact with much smaller objects (typically centimetre-sized), including natural fluctuations in leaves etc. This means that Carabas SAR images will be very stable and only change when metre-sized objects have been introduced or removed from the scene, and is otherwise unaffected by smaller-sized alterations.

Proven performance

Carabas's change detection techniques have been proven to be useful even on a year-to-year time scale. Microwave radar and higher frequencies will, on the other hand, experience significant background differences between subsequent images. These are so dominant that the use of a change detection scheme is useless in general scenarios in natural terrain. This means that even when it comes to automated detection of non-concealed targets, the Carabas frequencies provide superior performance.

The two pictures above show results from Saab's change detection algorithm operating on a recent Carabas image pair of a forest scene with and without a Land Rover present. The change image data finds the Land Rover as the most probable target position (95%), with competing false alarms having small probabilities (strongest competitor 4%, second strongest 0.4%, further false alarms with <0.4% probability). Compared with typical FOPEN performance figures, these results are exceptionally good. This information is utilized for displaying geopositioned target candidates, with metre accuracy, for the operator – preferably overlaid on a digital terrain map.

Emerging capabilities

The Carabas frequency bands and unique technological solutions are also very suitable for innovative applications neighbouring traditional FOPEN. Among possible extended capabilities, low frequency subsurface target detection (mines and IEDs) and low frequency GMTI (moving object - dismounts - detection under foliage) address key military requirements. For these Saab has concepts available, qualified by in depth studies as well as initial technical development.

Versatile capacity

The Carabas technology is also suitable for civilian operations such as, search and rescue, terrain topography mapping, forestry surveillance and biomass estimation, disaster monitoring, and surveillance of illegal activities.

In use

Proven and mature concept

The Carabas system concept has been continuously proven by the Swedish Defence Research Agency (FOI) since the early 1990s. The prototype platform Carabas II has participated in numerous military and civilian campaigns throughout four continents, with demonstrated and validated performance for foliage penetration, automatic target detection and counter-camouflage.

Based on these experiences, Saab is now introducing the third generation Carabas radar system. For customers’ evaluation of the technology and its capabilities, we are offering the Carabas FOPEN Demonstrator. This demonstrator system is a small tactical FOPEN system based on dual-band and dual-polarisation technology. Being simple to integrate on a small sized rotary wing aircraft, it is ideal for learning and evaluating the technology.

Technical specifications

CARABAS FOPEN Demonstrator

Saab is now introducing the Carabas FOPEN Demonstrator for customers’ evaluation of the technology and its capabilities. This demonstrator system is a small tactical surveillance system for integration on small rotary wing aircraft (concept proven on Schweizer 300C).

However, the flexible and scalable Carabas system concepts cover all types of aircraft of different sizes and operational profiles; manned and UAV, rotary or fixed-wing. The surveillance capacity of Carabas in the demonstrator configuration, 5 sq km per minute, is greatly enhanced when scaled to larger aircraft, for example when integrated to a regular business jet it expands to 5 sq km per second.